Thank you! I've been doing 3D art for about a decade now. I did all the work on the Octopus. My partner modeled a lot of the interior props, and he's been doing this less than a year.
Gamedev TV has some great beginner friendly courses. They're not free unfortunately, but they do go on sale often (even cheaper through humble bundle). Grant Abbitt is one of the teachers on the site, and he runs a youtube channel with a lot of free content for game modeling. Cherlynn Lima and Vertex Arcade are a couple other channels I like a lot.
Studying and trying to recreate the look of older 3D games is a good way to learn. As for texturing, I would say a good way to get better at that is to practice and learn more about drawing and painting in general. It's essentially applying 2D techniques to 3D surfaces. That and studying up on shader code. The Octopus was hand (well, mouse) painted in Blender, and I coded a shader in Godot to give it roughness and rim lighting. A lot of the ship assets were textured completely procedurally with godots shaders. Noise textures in particular are incredibly versatile.
I animated this Octopus with the rigify add on in blender. The channel CGDive has very in depth tutorials on that, but rigify is a lot to learn. So I would say start by learning to make basic armatures (Royal skies is a good channel for that), and using shape keys.
3D art is a mix of a lot of different disciplines. There's always more to learn (even after a decade I am always learning new things). The internet has a lot of great resources (but also a lot of 3D tutorials that are not applicable to gamedev). I actually have a degree in 3D art and animation, but I have learned far more online than from university. The official documentation for godot and blender are super helpful as well. This is a really long answer, and I could honestly say a lot more. But my biggest advice is to keep practicing and setting goals for yourself.